@RL_Dane @trashheap another one #FreeBSD on the laptop user here :-).
FWIW OpenBSD has a ports system too: https://www.openbsd.org/faq/ports/ports.html
It's not quite like AUR (I think, not overly familiar with it), in that the ports tree is 'official', though it is separate from the base system. A committer can have a commit bit permission for base but not for ports, or the other way around, or for both, anyone can contribute patches or new ports, but in the end a ports committer has to add them to the tree.
@RL_Dane @trashheap as the #OpenBSD FAQ mentions, it is a set of makefiles containing patches and instructions on how to package software for the OS.
Then with that, both #OpenBSD and #FreeBSD (each with their respective ports tree) produce pre-compiled binary packages which is what most users interact with.